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Respiratory ß-2-Microglobulin exerts pH dependent antimicrobial activity

Authors
  • Holch, Armin1
  • Bauer, Richard1
  • Olari, Lia-Raluca1
  • Rodriguez, Armando A.2, 3
  • Ständker, Ludger2
  • Preising, Nico2
  • Karacan, Merve2
  • Wiese, Sebastian3
  • Walther, Paul2
  • Ruiz-Blanco, Yasser B.4
  • Sanchez-Garcia, Elsa4
  • Schumann, Christian5
  • Münch, Jan1, 2
  • Spellerberg, Barbara1
  • 1 University Hospital, Germany , (Germany)
  • 2 Ulm University Medical Center, Germany , (Germany)
  • 3 Ulm University, Germany , (Germany)
  • 4 Center of Medical Biotechnology, University of Duisburg-Essen, Germany , (Germany)
  • 5 Sleep and Respiratory Critical Care Medicine, Clinics Kempten-Allgäu, Kempten and Immenstadt, Germany , (Germany)
Type
Published Article
Journal
Virulence
Publisher
Landes Bioscience
Publication Date
Oct 22, 2020
Volume
11
Issue
1
Pages
1402–1414
Identifiers
DOI: 10.1080/21505594.2020.1831367
PMID: 33092477
PMCID: PMC7588194
Source
PubMed Central
Keywords
License
Green

Abstract

The respiratory tract is a major entry site for microbial pathogens. To combat bacterial infections, the immune system has various defense mechanisms at its disposal, including antimicrobial peptides (AMPs). To search for novel AMPs from the respiratory tract, a peptide library from human broncho-alveolar-lavage (BAL) fluid was screened for antimicrobial activity by radial diffusion assays allowing the efficient detection of antibacterial activity within a small sample size. After repeated testing-cycles and subsequent purification, we identified ß-2-microglobulin (B2M) in antibacterially active fractions. B2M belongs to the MHC-1 receptor complex present at the surface of nucleated cells. It is known to inhibit the growth of Listeria monocytogenes and Escherichia coli and to facilitate phagocytosis of Staphylococcus aureus . Using commercially available B2M we confirmed a dose-dependent inhibition of Pseudomonas aeruginosa and L. monocytogenes . To characterize AMP activity within the B2M sequence, peptide fragments of the molecule were tested for antimicrobial activity. Activity could be localized to the C-terminal part of B2M. Investigating pH dependency of the antimicrobial activity of B2M demonstrated an increased activity at pH values of 5.5 and below, a hallmark of infection and inflammation. Sytox green uptake into bacterial cells following the exposure to B2M was determined and revealed a pH-dependent loss of bacterial membrane integrity. TEM analysis showed areas of disrupted bacterial membranes in L. monocytogenes incubated with B2M and high amounts of lysed bacterial cells. In conclusion, B2M as part of a ubiquitous cell surface complex may represent a potent antimicrobial agent by interfering with bacterial membrane integrity.

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